I view this as "Al Jefferson versus Paul Millsap" if we buy the notion that a team should like to hang on to the better guy. The Jazz have two almost completely equal players with role overlap. It's a highly unusual sports situation and a fun one to unpack (well, at least in my opinion).
They are both 27 years of age and both ill-suited to be anything other than a power forward defensively. Al Jefferson is technically a center, but he's a bad enough shot-blocker to the point where it's an ill-fitting role (more on this later).
Paul Millsap is considerably shorter but excels with superior quickness, athleticism and strength. This is as good a time as any to show Millsap making Antawn Jamison look completely foolish.
Al Jefferson is somehow more bruising and more refined, all at once. He's the most skilled post player in basketball, a descriptor that used to mean something. Though Big Al is a fine offensive player and a help to this Jazz team, post play now means less than it ever did.
The allowance of zone defense has de-emphasized the plodding post player in favor of fast, versatile three-point shooters. In the '90s, someone like Jefferson could easily catch the ball and back his man down. Today, Jefferson is regularly fronted and swarmed. He makes do with the circumstances, but his effectiveness is quite compromised by basketball modernity.
Thankfully for Al, he has more skills than just post moves and touch. Jefferson can shoot well from outside, allowing for his inclusion in "pick-and-pops." He's also a rugged rebounder at an 11.3 per 40 minute average.
Paul Millsap will never be confused for a post-play savant. He gets his points via quick dribbles to the rim but also with points off rebounds.
At this point, with what we've discussed, you might give the edge to Big Al on account of size. There are two factors that swing this debate wildly in Millsap's favor.
First, Al Jefferson is an awful defender. Though blessed with height and length, he reacts too slowly to make it matter. Millsap may be undersized, but Jefferson is worse for being under-fast (to invent a term). Teams usually perform far worse defensively when Al Jefferson is on the court, and the Utah Jazz (via BasketballValue.com) were no exception last season.
The second factor is that Paul Millsap makes nearly half as much (roughly $8 million to Jefferson's $15 million). Between Millsap's relative cheapness and superior defensive play, I'm going to have to side with the little guy on this.